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Expression of phosphoenolpyruvate carboxylase and phosphoenolpyruvate carboxylase kinase genes. Implications for genotypic capacity and phenotypic plasticity in the expression of crassulacean acid metabolism

Lookup NU author(s): Dr Tahar Taybi, Professor Anne Borland

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Abstract

In plants with crassulacean acid metabolism (CAM), dark CO2 uptake is mediated by phosphoenolpyruvate carboxylase (PEPC), an enzyme that can be regulated at transcriptional and posttranslational levels. Reversible phosphorylation of PEPC is catalyzed by a dedicated PEPC kinase, which in turn is regulated at the transcriptional level over the 24-h cycle in CAM plants. PEPC kinase controls the day/night regulation of PEPC during the CAM cycle, thus facilitating plasticity for optimizing CO2 uptake under different environmental conditions. To understand the importance of PEPC kinase in relation to its target PEPC in terms of CAM performance, the expression of the genes encoding the two enzymes was investigated in four species of Clusia that have photosynthetic patterns ranging from C3 photosynthesis to constitutive CAM. By linking changes in the expression of PEPC and PEPC kinase to day/night patterns of leaf gas exchange, organic acid, and soluble sugar contents under different environmental conditions, the genetic and metabolic limitations to CAM plasticity were assessed. The results indicate that PEPC expression is a major factor underpinning the genotypic capacity for CAM and that PEPC kinase expression does not appear to limit CAM. The day/night regulation of Ppck transcript abundance was found to be a consequence of CAM and the day/night cycling of associated metabolites, rather than the primary controlling factor for the temporal separation of carboxylation processes.


Publication metadata

Author(s): Taybi T, Nimmo HG, Borland AM

Publication type: Article

Publication status: Published

Journal: Plant Physiology

Year: 2004

Volume: 135

Issue: 1

Pages: 587-598

ISSN (print): 0032-0889

ISSN (electronic): 1532-2548

Publisher: American Society of Plant Biologists

URL: http://dx.doi.org/10.1104/pp.103.036962

DOI: 10.1104/pp.103.036962

PubMed id: 15133148


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